Polystyrene frequency

Whether or not a polymer is rubbery or glass-like depends on the relative values of t and v. If t is much less than v, the orientation time, then in the time available little deformation occurs and the rubber behaves like a solid. This is the case in tests normally carried out with a material such as polystyrene at room temperature where the orientation time has a large value, much greater than the usual time scale of an experiment. On the other hand if t is much greater than there will be time for deformation and the material will be rubbery, as is normally the case with tests carried out on natural rubber at room temperature. It is, however, vital to note the dependence on the time scale of the experiment. Thus a material which shows rubbery behaviour in normal tensile tests could appear to be quite stiff if it were subjected to very high frequency vibrational stresses. 

Poly(methyl methacrylate) is a good electrical insulator for low-frequency work, but is inferior to such polymers as polyethylene and polystyrene, particularly at high frequencies. The influence of temperature and frequency on the dielectric constant is shown in Figure 15.9. 

From an analysis of data for polypyrrole, Albery and Mount concluded that the high-frequency semicircle was indeed due to the electron-transfer resistance.203 We have confirmed this using a polystyrene sulfonate-doped polypyrrole with known ion and electron-transport resistances.145 The charge-transfer resistance was found to decrease exponentially with increasing potential, in parallel with the decreasing electronic resistance. The slope of 60 mV/decade indicates a Nemstian response at low doping levels. 

Rouse behavior observed on PI homopolymer melts has to be modified if the labelled (protonated) PI species are replaced by diblock copolymers of proto-nated PI and deuterated polystyrene (PS) [46]. The characteristic frequency Q(Q) is slowed down considerably due to the presence of the non-vanishing X-parameter. Thus, the reduction is stronger at smaller Q-values or at larger length scales than in the opposite case. In addition, as a minor effect, Q(Q) becomes dependent on both friction coefficients per mean square monomer length, //2, valid for PI and for PS. 

The total optical path difference between the two arms of the interferometer, for a sample length of about 50 mm, is of the order of 10 mm or less, minimizing the systematic error due to laser frequency fluctuations. To reduce the thermal effects on the interferometer assembly, the interferometer support plate is stabilized to a temperature slightly higher than room temperature and insulated from air currents by a polystyrene foam shield. The temperature variation of the interferometer support is kept below 0.1 K. 

Figure 5.18 The high frequency shear modulus versus volume fraction for a polystyrene latex for three different electrolyte concentrations. The symbols are the experimental data and the solid lines are calculated fits using a cell model. The radius of the latex particles was 38 nm...

The MWCNT-filled polystyrene composites have good electromagnetic interference shielding properties (Snow and Perkins, 2005). The shielding effectiveness of MWCNT-filled composites was frequency independent, and increased with the... 

Polystyrenes have weak loss factors, about 1-30 X 10 , and do not heat up under high-frequency current. They cannot be welded by this technique. 

The ultrasonic degradation of polystyrene in benzene increases with a decrease in the applied ultrasonic frequency (see Section 2.6.1). 

Melville and Murray have investigated the degradation of polystyrene in toluene, albeit in vacuo and at a slightly lower insonation frequency (213 kHz) and compared their results with those obtained by Schmid (300kHz) at 15 atm (Tab. 5.9). 

Figure 2. Frequency distributions for polystyrene initiated with n-BuLi.

A. Jones Yes, I didn t show all the data. Most of the data is from the literature. Polystyrene data and polyisobutylene data at two field strengths can be accounted for by these lattice models based upon the three bond jump. Some recent data by Dr. Bovey on the polybutene was more difficult to fit with regard to the frequency dependence. (F. C. Schilling, R. E. Cais and F. A. Bovey, Macromolecules ]A, 325 (19T8).) Frequency dependent data I think is important information to acquire when trying to understand the dynamics. 

The power factor is the energy required for the rotation of the dipoles of a polymer in an applied electrostatic field of increasing frequency. Typical values vary from 1.5 x 10 for polystyrene to 5 x 10 for plasticized cellulose acetate. Values increase at Tg and because of the increased chain mobility gained so that Tg and Tm have been measured using differences in the power factor as temperature is increased. 

---